The class of polymers of carbon monoxide and olefin(s) has been known for some time. Brubaker, U.S. Pat. No. 2,495,286, produced such polymers of relatively low carbon monoxide content in the presence of free radical initators, e.g., peroxy compounds. G.B. 1,081,304 produced similar polymers of higher carbon monoxide content in the presence of alkylphosphine complexes of palladium salts as catalyst. Nozaki extended the reaction to produce linear alternating polymers in the presence of arylphosphine complexes of palladium moieties and certain inert solvents. See U.S. Pat. No. 3,694,412, for example.
More recently, the class of linear alternating polymers of carbon monoxide and at least one ethylenically unsaturated hydrocarbon has become of greater interest in part because of the greater availability of the polymers. The more recent processes for the production of such linear alternating polymers, now known as polyketones or polyketone polymers, are illustrated by a number of published European Patent Application including 121,965, 181,014, 214,671, and 257,663 U.S. Pat. No. 4,899,462 as well as U.S. Pat. No. 4,965,341. The process typically involves the use of a catalyst composition formed from a compound of palladium, cobalt or nickel, the anion of a strong non-hydrohalogenic acid and a bidentate ligand of phosphorus, nitrogen or sulfur. The resulting linear alternating polymers are of relatively high molecular weight and are thermoplastic, being processed into articles of established utility by methods conventional for thermoplastics.
The actual polymerization process is conducted by a variety of procedures. In one embodiment, the process is conducted in a batchwise manner as by charging the monomeric reactants, catalyst composition and a reaction diluent to a suitable reactor and maintaining the reactor and contents at a suitable polymerization temperature. As such a batchwise polymerization proceeds, the pressure will drop, the concentration of the polymerization product in the diluent increases and the viscosity of the suspension of insoluble polymer in the reaction diluent also increases. In effect, the reaction temperature is the only reaction variable that remains constant. In a second embodiment, the process is conducted in a semicontinuous manner in which the reaction pressure is also kept constant by continuous addition of monomer to the reactor during polymerization. In these process modifications, the changes that do occur in the reaction variables result in a product of somewhat variable properties.
A better control over the product properties is obtained if the polymerization process is conducted in a continuous manner. In this embodiment, the monomeric reactants, the catalyst composition and reaction diluent are continuously added to the reaction zone. After an induction period in which the concentration of polymer in the suspension of polymer in the reaction diluent increases, a steady state is reached in which the polymer suspension is removed from the reaction zone at a rate substantially equivalent to the rate at which it is produced. As a result, the temperature, pressure, liquid volume and concentration of polymer in the suspension of polymer in reaction diluent are all kept relatively constant. A continuous type of process wherein the reaction variables are constant is easier to automate and therefore offers considerable practical advantages.
In published European Patent Application 305,011 such a continuous-type polymerization process is described. The disclosed process, however, takes place in a single polymerization reactor. It would be of advantage to provide an improved continuous process for the production of linear alternating polymers of carbon monoxide and at least one ethylenically unsaturated hydrocarbon.